Outdo last in tournament, bottom (5)
I believe the answer is:
trump
'outdo' is the definition.
('trump' can be a synonym of 'outdo')
'last in tournament bottom' is the wordplay.
'last in' suggests the final letters.
'bottom' becomes 'rump' ('rump' can be a synonym of 'bottom').
The final letter of 'tournament' is 't'.
't'+'rump'='TRUMP'
(Other definitions for trump that I've seen before include "Brick" , "take trick" , "Surpass" , "club perhaps" , "Trusty fellow (colloq.); ruff" .)